Welcome to the most tumultuous summer of the 20th century. It's 1969, and for the Levin family, the times they are a-changing. Every year, the children have looked forward to spending the summer at their grandmother's historic home in downtown Nantucket. But like so much else in America, nothing is the same.

After a string of bad dates and no prospects, Sophia Othonos has finally hit the jackpot: an actual nice guy. When he suggests a romantic getaway, she’s sure they’re about to take the next step toward their future. A rustic cruise to the Galápagos Islands isn’t exactly her idea of a vacation, but Sophia is ready for anything…until her boyfriend has to cancel. Now she’s all alone on a trip that was meant for two. Sophia finds herself at a crossroads about who she is, what she wants, and whether her relationship is really everything she thought.

When Mallory Blessing's son, Link, receives deathbed instructions from his mother to call a number on a slip of paper in her desk drawer, he's not sure what to expect. But he certainly does not expect Jake McCloud to answer. It's the late spring of 2020 and Jake's wife, Ursula DeGournsey, is the frontrunner in the upcoming Presidential election. There must be a mistake, Link thinks. How do Mallory and Jake know each other?

After uprooting her life in the States, Irene Steele has just settled in at the villa on St. John where her husband Russ had been living a double life. But a visit from the FBI shakes her foundations, and Irene once again learns just how little she knew about the man she loved. With help from their friends, Irene and her sons set up their lives while evidence mounts that the helicopter crash that killed Russ may not have been an accident.

Fresh off a bad breakup with a longtime boyfriend, Nantucket sweetheart Lizbet Keaton is desperately seeking a second act. When she’s named the new general manager of the Hotel Nantucket, a once Gilded Age gem turned abandoned eyesore, she hopes that her local expertise and charismatic staff can win the favor of their new London billionaire owner, Xavier Darling, as well as that of Shelly Carpenter, the wildly popular Instagram tastemaker who can help put them back on the map.

Claire has a problem with setting limits. All her life she has taken on every responsibility, assumed every burden, granted every request. Claire wants it all—and in the eyes of her friends, she has it: a devoted husband, four beautiful children, even a successful career as an artist. So when she agrees to chair the committee for Nantucket's social event of the year, she knows she can handle it. Claire can handle anything. But when planning the gala propels her into the orbit of billionaire Lock Dixon, unexpected sparks begin to fly.

Kelley Quinn is the owner of Nantucket's Winter Street Inn and the proud father of four, all of them grown and living in varying states of disarray. Patrick, the eldest, is a hedge fund manager with a guilty conscience. Kevin, a bartender, is secretly sleeping with a French housekeeper named Isabelle. Ava, a school teacher, is finally dating the perfect guy but can't get him to commit. And Bart, the youngest and only child of Kelley's second marriage to Mitzi, has recently shocked everyone by joining the Marines.

On a perfect June day, Vivian Howe, author of 13 beach novels and mother of three nearly grown children, is killed in a hit-and-run car accident while jogging near her home on Nantucket. She ascends to the Beyond where she's assigned to a Person named Martha, who allows Vivi to watch what happens below for one last summer. Vivi also is granted three “nudges” to change the outcome of events on earth.

Birdie Cousins has thrown herself into the details of her daughter Chess's lavish wedding, from the floating dance floor in her Connecticut back yard to the color of the cocktail napkins. Like any mother of a bride-to-be, she is weathering the storms of excitement and chaos, tears and joy. But Birdie, a woman who prides herself on preparing for every possibility, could never have predicted the late-night phone call from Chess, abruptly announcing that she's cancelled her engagement. It's only the first hint of what will be a summer of upheavals and revelations.

Adrienne Dealey has spent the past six years working for hotels in exotic resort towns. This summer she has decided to make Nantucket home. Left flat broke by her ex-boyfriend, she is desperate to earn some fast money. When the desirable Thatcher Smith, owner of Nantucket's hottest restaurant, is the only one to offer her a job, she wonders if she can get by with no restaurant experience. Thatcher gives Adrienne a crash course in the business...and they share an instant attraction.